 Good day everybody. This is Dr. Sanjay Sanyal, Professor of Department Chair. So this is going to be a demonstration of the Karate Triangle. This is Subangadabur. This is the right side. We have completely exposed the following structures. Antiaservical region, lateral cervical region, the root of the neck. We have removed the clavicle. We have removed the ramus of the mandible. And we are even showing the in front temporal force on the right side. So let's start from here. The Karate Triangle is mounted by the sternocleidomastoid which we have dissected out. Pustearly, superiorly it is bounded by the posterior belly of the digastric. In this particular cadaver, we cannot see the style of hyoid. And inferiorly it is bounded by the superior belly of the homohyoid. So therefore this is the Karate Triangle. It was roofed over by the Pritismal muscle which has been removed and the floor was composed of the muscular component of the predracheal fascia. Now let's take a look at the contents. The most important contents are this one here. This is the internal jugular vein. Normally we have seen that the large veins are medial to the artery but in this case the neck, the internal jugular vein is lateral to the artery. This is the common carotid artery which is bifurcated in the internal and external carotid arteries which I shall describe just now. And the posterior aspect is this nerve here. This is the vagus nerve. These three structures were completely enclosed by one tough sheath called the carotid sheath. This carotid sheath is derived from three layers of deep cervical fascia. The prevertible layer of deep cervical fascia, posteriorly from the prevertible layer of deep cervical fascia and medially from the predracheal layer of deep cervical fascia with components also from the ilar fascia. We have completely removed that also. So let's start with the internal jugular vein first. The internal jugular vein is this one here as I told you. It starts from the base of the skull. High up here, it emerges through the jugular foramen and there's a bulb which is called the superior bulb of the internal jugular vein. It's a continuation of the sigmoid sinus and just at the beginning when it is forming this superior bulb of the internal jugular vein and there's a valve also, it receives the atria-patriotus sinus. Then the internal jugular vein descends down. It receives tributaries in the neck corresponding to the branches of the carotid artery and it continues all the way down and here we can see it opens into the subclavian vein. The subclavian vein and the internal jugular vein they unite at this point which is at the level of the sternoclavical joint. We have removed the clavicle. This is called the pyrogeof angle or the venous angle and then it becomes continuous as the brachiocephalic vein. So this is the right side. So this is the full course. Just before it enters there can be another small dilatation which is called the inferior bulb of the internal jugular vein and that is also associated with the valve. The internal jugular vein is a very useful site for cardiac catheterization. The puncture is done medial to the sternoclear mastoid and the needle is directed downwards and we can enter into the right atrium of the heart for various procedures that is called cardiac catheterization. So this is a very useful route for cardiac catheterization. Now let's take a look at the next structure here. This is the common carotid artery. In this particular case because it's the right side the common carotid artery is arising from the brachiocephalic trunk. So this is the brachiocephalic trunk here and we can see the brachiocephalic trunk is dividing into the right subclavian and the common carotid, right common carotid. You can see there's a big opening here. This was the place where they had done the embombing and that's the reason why this place has been punctured and that's why there's been extravization of blood. The common carotid artery runs on the middle side of the internal jugular vein and approximately at the level of the upper border of the thyroid cartilage, it divides into an external carotid and internal carotid. Internal carotid artery I should describe just now. First let me finish with the external carotid. It is called external carotid because it supplies all the structures outside the skull. Of course there are two exceptions that I shall mention briefly later. So this is the external carotid artery. The external carotid artery, it runs under the posterior belly of the digustric. You can see that here. And this external carotid artery typically gives six branches. We can see five of those branches. So let's take a look at the branches of the external carotid artery. We can see three branches here. One, two, three. This is the superior thyroid artery and you can see it is going down and entering into the upper pole of the thyroid gland. This superior thyroid artery is accompanied by this nerve here. This is the external laryngeal nerve. When we are doing surgery of the thyroid gland, this nerve is likely to be injured. The next branch that you can see here is the lingual artery. The lingual artery enters into the tongue deep to the hypoglossus muscle. And you can see it is accompanied by the hypoglossal nerve. And this inside the tongue, the lingual artery divides into three main branches. The dorsal lingual artery, the deep lingual artery and the sublingual artery. The next branch is this one here. This is the facial artery. The facial artery, it makes a loop under the mandible and then it gives branches to the pallet, ascending palletine into the console and then it comes back down here and we can see the remaining portion of the facial artery here. As it's coming down, it makes a deep groove on the posterior aspect of this, so the mandible or gland and we can see that also here. And then it runs in a very tortuous fashion on the side of the face and we can see that portion here. So this is the third branch, the facial artery. We can palpate the facial artery against the inferior border of this mandible here just in front of the mesetra muscle. These are three anterior branches. Now let's take a look at the medial branch. This is the medial branch. This is the ascending pharyngeal artery. The ascending pharyngeal artery runs up on the side of the pharynx and it gives basically two sets of branches. One set of branches are called the pharyngeal branches. The pharyngeal branches are the ones which supply all the pharyngeal constrictors, superior, middle and inferior pharyngeal constrictor. And the other branches are called the meningo vascular branches which supply the meninges of the posterior cranial fossa and also supplies the lower four cranial nerves. This ascending pharyngeal artery, though it's quite small, is an important artery. That's the fourth branch. Coming to the remaining two branches, we can see only part of it. So this is the continuation of the external carotid artery. As it passes under the stylohyide and the stylo-pustiability of the gastric, it enters into the parotid gland. We have removed the parotid gland here so therefore this was the course inside the parotid gland. And there it gives this branch here. So we can see, typically, it should give a branch below the pustiability of the gastric and a branch above the pustiability of the gastric. But here it is not doing so. Here it is giving only a common branch and that is further dividing into two. The one upper one is called the posterior auricular artery. The lower one which should run along the lower border of the pustiability of the gastric, that is the occipital artery. The occipital artery is the one which runs up to the scalp like this and it goes across the apex of the posterior lateral cervical region. That's why the lateral cervical region apex is called occipital triangle. So these are the final two branches, the six branches of the external carotid artery. And thereafter what does the external carotid artery do? Inside the parotid gland it divides into this branch here. This is the maxillary artery. And you can see it is entering into the infratemple fossa. This is the infratemple fossa. And inside the infratemple fossa it has got three parts which you have already described in another section and it gives a total of 15 branches. And the smaller terminal division is this one here. This is the superficial temporal artery which runs across the front of the tragus of the ear, across the zygomatic arch which we have cut where we can feel its pulsation and then it supplies the skin of the temporal scalp and we can see that running in the superficial temporal fascia here. So this is the complete course and the termination of the external carotid artery. As I said, external carotid artery supplies all structures outside but it has got two exceptions and one of that exception we can see here. The maxillary artery, it is giving this branch here. This is the middle meningeal artery. The middle meningeal artery enters into the cranial cavity, middle cranial fossa through the foramine spinosum and it supplies the meninges of the cranial cavity. So therefore that is an exception and there should be an accessory meningeal artery that enters through the foramine avail but we cannot see that here. So this is the full course of the external carotid artery. Now let's take a look at internal carotid artery, whatever we can see here. The internal carotid artery is called internal carotid because it supplies all the structures inside the cranial cavity. Again there is an exception. It is an anterior circulation of the circle of Willis. How do we recognize the internal carotid artery by this dilatation here? This is the carotid sinus. Inside it has got receptors, there is a paroreceptor. The internal carotid artery runs up. This portion is called the cervical part. And here in this particular cadaver we can see something very unique. We can see that the internal carotid artery is highly tortuous here. This is called dolicoectasia and we can see that tortuosity here very clearly. This is the tortuous part. And then it enters into the carotid canal in the Petrus temporal bone. That is called the Petrus part. And then it enters into the middle cranial fossa. That is the cavernous part. And then it becomes the intracerebral part. Which divides into anterior and middle cerebral arteries. So this is the internal carotid artery. Coming back to this carotid sinus. This carotid sinus and there is a small body here which is called the carotid body. They are respectively the paroreceptor and chemoreceptor, the peripheral chemoreceptor. They are supplied by branches of glossophageal nerve. And they immediate what is known as the carotid sinus reflex. So when we are palpating in the neck we should not palpate in the carotid triangle because we might produce carotid sinus syncope if a person is hypersensitive. That brings me to some clinical applications of the carotid artery as a whole. When we are seeing a person who is unconscious on the side of the road we have to determine whether the person is alive or the person is dead. We should palpate for the common carotid artery below the superior belly of the hormone, approximately at this level. We do not palpate in the carotid triangle proper. That is called central carotid pulsation. The carotid artery is a very common site of occlusion and we can feel in this particular cadabra also it has got some calcified material on the tunica media. Carotid angioplasty, carotid Doppler, carotid endartrectomy, all these are commonly performed procedures in the carotid artery. Common carotid and internal carotid artery. And this occlusion of the intercarotid artery produces stroke as we all know. So that is the next important content of the carotid sheath. And finally coming to the last part of the carotid sheath is this big nerve here. This is the nerve, this is the vagus nerve. Content, this runs on the posterior aspect of the sheath behind these two vessels. It comes out through the jugular ferrament and as it runs down it goes across and it crosses the subclavian artery. We can see that it's crossing the subclavian artery and then it will give branches called the recurrent laryngeal nerve which we shall show in another description. While it is running down we can see two important branches that it gives. We can see this branch here. This is the superior laryngeal nerve and the superior laryngeal nerve I've shown from this side also it divides into an internal laryngeal nerve which pierces the thyroid in my brain and the external laryngeal nerve which accompanies the superior thyroid artery which I had mentioned just a little while back. The vagus nerve has got many branches but we can see only these branches in this particular dissection. So these are the three important contents of the carotid sheath and the carotid triangle. That's all for now that I wanted to show you. Dr. Sanjeev is signing out. Mr. Solomon is the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day. Please like and subscribe.